Rolling is a metal forming process in which stock sheets or strips are passed through at least one pair of rolls. Tandem rolling mills are configured so the rolling is performed in one pass through more than one pair of rolls instead of multiple passes through one pair of rolls. A tandem rolling mill includes at least two stands, each stand having at least one work roll pair that rolls the material to reduce the thickness of the material. Specifically, the material is rolled between the work roll pair so that it moves from a thicker gauge to a thinner gauge. The interaction between the work rolls and the material is sometimes referred to as the roll bite. The stands are placed in sequence such that the reductions are done successively. Tandem mills can be either hot or cold rolling mill types.
Some tandem rolling mills include backup rolls that provide rigid support to the work rolls and therefore allow the diameter of the work rolls to be reduced. Tandem rolling mills have a variety of configurations and can be two-high, three-high, four-high, six-high and so forth. A two-high roll may have two work rolls, each located on opposite sides of a strip of metal. A four-high roll may have four rolls, including two work rolls located on opposite sides of a strip of metal, and two backup rolls, each located on opposite sides of a work roll from the strip of metal.
After the stock sheets or strips pass through the tandem rolling mill, the final product can be either a coil of metal or a slab of metal, depending on the end use of the material. After undergoing the rolling process, the material generally has a temperature that is greater than room temperature due to heat generated during the rolling process, unless the material is exposed to a cooling process after the roll bite. The exit temperature of the material is a variable that must be carefully monitored and controlled, as the exit temperature of the material directly affects the material's mechanical properties.